How to calculate fence square footage
Fence square footage is the face area of the fence — the flat surface you actually see and coat. The math is simply length times height, but the two numbers trip people up in opposite ways. Height is easy: measure from the ground to the top of the boards, usually 4, 6, or 8 feet. Length is where mistakes happen, because a yard rarely has one straight fence. Walk the whole perimeter, measure every straight section separately, and add them together for the total run before you multiply.
Once you have the total length and height, multiply them for the area of one face. A 100-foot fence at 6 feet tall is 600 square feet on a single side. That figure is all you need if you're only coating the side that faces your yard — but most people finish both faces, which is where the next step comes in.
One side or both — and how much stain to buy
Deciding whether you're coating one face or two is the single most important choice for your material estimate, because doing both sides doubles the square footage. Our 600-square-foot fence becomes 1,200 square feet the moment you commit to staining the neighbor's side as well. Divide that total by your product's coverage rate to get gallons: at roughly 175 square feet per gallon, 1,200 square feet needs about 7 gallons for one coat.
Coverage is a range, not a fixed number, because it depends on the wood. Smooth, previously sealed boards might stretch a gallon to 200 square feet, while rough-sawn, bare, or sun-bleached wood can drink it down to 150 square feet or less — and often needs a second coat. When you're comparing paint/stain products, read the label's coverage rate and lean toward the lower number for older fences so you don't run out mid-project.
Privacy fences vs. picket fences
Solid privacy fences are a clean rectangle: the boards butt together with no gaps, so the full length × height area is what you coat. Picket fences are different — the gaps between pickets mean a chunk of that rectangle is empty air. For a rough picket estimate, use the ratio of picket width to picket spacing to reduce the face area, then remember the sides and edges of each picket still need coating, which claws some of that area back. When in doubt, measure the full rectangle for a safe over-estimate.
The same face-area approach works for other exterior surfaces. If you're also finishing the house, the siding calculator handles walls the same way — length times height, minus openings — so you can budget the whole exterior project from one set of measurements.